Activist investor Starboard Value disclosed a 9% stake in Tripadvisor on Thursday and said the stock was undervalued.

On Thursday, Starboard Value disclosed a 9% ownership stake in Tripadvisor’s stock of just under 10.64 million shares, or about$159.4 million based on the stock’s closing price of $14.99 a share on Wednesday.

While Tripadvisor posted better-than-expected results in the first quarter, its core business remains under pressure from factors including increased competition and weaker travel demand.